| Summary: | Validation studies conducted within a food processing facility using surrogate organisms could better represent the manufacturing process than controlled laboratory studies with pathogenic bacteria on precision equipment in a BSL-2 lab. The objectives of this project were to examine potential surrogate bacteria during biltong processing, conduct biltong surrogate validation lethality studies, and measure critical factors and intrinsic parameters during processing. Beef pieces (1.9 cm × 5.1 cm × 7.6 cm) were inoculated with four-strain mixtures of <i>Carnobacterium</i> <i>divergens/C. gallinarum</i>, <i>Pediococcus acidilactici/P. pentosaceous</i>, and Biotype 1 <i>E. coli</i> ATCC BAA (-1427, -1428, -1429, and -1430), as well as a two-strain mixture of <i>Latilactobacillus sakei</i> and other commercially available individual bacterial cultures (<i>P. acidilactici</i> Saga200/Kerry Foods; <i>Enterococcus faecium</i> 201224-016/Vivolac Cultures). Inoculated beef was vacuum-tumbled in marinade and dried in a humidity-controlled oven for 8–10 days (24.9 °C; 55% relative humidity). Microbial enumeration of surviving surrogate bacteria and evaluation of intrinsic factors (water activity, pH, and salt concentration) were performed post inoculation, post marination, and after 2, 4, 6, 8, and 10 days of drying. Trials were performed in duplicate replication with triplicate samples per sampling time and analyzed by one-way RM-ANOVA. Trials conducted with <i>E. faecium</i>, <i>Pediococcus</i> spp., and <i>L. sakei</i> never demonstrated more than 2 log reduction during the biltong process. However, <i>Carnobacterium</i> achieved a >5 log (5.85 log) reduction over a drying period of 8 days and aligned with the reductions observed in previous trials with pathogenic bacteria (<i>Salmonella, E. coli</i> O157:H7, <i>L. monocytogenes</i>, and <i>S. aureus</i>) in biltong validation studies. Studies comparing resuspended freeze-dried or frozen cells vs. freshly grown cells for beef inoculation showed no significant differences during biltong processing. <i>Carnobacterium</i> spp. would be an effective nonpathogenic in-plant surrogate to monitor microbial safety that mimics the response of pathogenic bacteria to validate biltong processing within a manufacturer’s own facility.
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